The present invention relates generally to router constructions and more particularly to plunge type router constructions which include an adjustable cutting depth stop system and a depth locking system.
Plunge type routers are similar to conventional routers in that they include a driving motor having a bit or cutting tool holding chuck secured to one end of the motor drive shaft which motor is axially movably supported with a base housing. However, while in conventional non-plunge type routers, the motor is locked in position relative to the base housing such that the cutting tool or bit projects axially outwardly from the workpiece engaging surface of the base housing to the desired depth of cut at all times, the plunge type routers provide biasing means which operate to retract the cutting tool or bit into the base housing during periods of non-use. In order to enable the router to be "plunged" to the desired cutting depth, such plunge type routers are also commonly provided with adjustable depth stop systems and may also include means for locking the motor housing at preselected position such as the cutting depth.
In one common construction for plunge type routers the motor housing is movably positioned and supported on a pair of guide bars extending generally perpendicularly upwardly from a work engaging flange member. An adjustable depth stop system includes a relatively smooth third bar or rod member adjustably secured to the motor housing such that the lower end thereof will engage a portion of the work engaging flange portion. In some designs, a turret may be provided on the flange member, the turret having a plurality of surfaces the height of which may be adjusted so that the depth of cut may be changed from a first preselected value to another preselected value by rotation of the turret so as to bring a different height surface into position for engagement by the preset bar or rod. However, while this type of system offers the advantage of being able to initially "program" the router for a plurality of depths of cut, it is difficult to exert a sufficient clamp force on the smooth bar or rod to prevent slight movement thereof during extended use. Of course, any movement of the guide bar relative to the motor housing will result in an error in each of the cutting depths for which the turret surfaces have been set. Also, in some of these designs, no measuring device is provided by which to gauge the setting of the guide bar or turret surfaces. Further, on those providing some form of scale, it is common to fixedly attach the scale to the motor housing. Thus, when a new cutting tool is fitted to the router, it is necessary to perform a calibration step in order to obtain the scale reading for a zero depth of cut and then mathematically compute the actual scale setting corresponding to the desired depth of cut.
It is also common to provide a depth lock system on plunge type routers which may be actuated to lock the motor housing in a desired position relative to the flange member such as the desired cutting depth thereby enabling the operator to concentrate on insuring proper tracking of the router without concern as to maintaining sufficient downward pressure on the motor housing to maintain the desired depth of cut. However, in the designs described above, the depth lock system comprises clamping means which typically engage only one of the two support and guide bars. This unbalanced locking system leaves the motor secured at only one point and may result in undesirable movement thereof during a cutting operation particularly when the direction of movement of the router is changed. Also, the likelihood of movement resulting may increase substantially over time as the relative small diameter guides do not afford a substantial wear surface for the repeated reciprocable movement of the motor housing.
The present invention, however, provides a plunge type router which substantially reduces the aforementioned problems associated with present designs. The router of the present invention provides an easily and conveniently readily adjustable depth stop system which may be easily calibrated to a zero setting on a scale associated with the adjustment means thus enabling any desired cutting depth to be merely "dialed" in. Further, the depth stop system utilizes a positive acting rack and pinion drive system for moving the stop means which allows smooth fine tuning of the desired cutting depth. Further, a clamping arrangement associated with the depth stop system enables a substantial clamping force to be exerted on the stop member so as to retain it in position during repeated operations and also the easily read scale associated with the pinion drive provides a quick means to verify the cutting depth.
The router of the present invention also includes a positive acting depth lock system which exerts a clamping force directly on the motor housing which clamping force is distributed over substantial circumferential surface of the motor housing thereby preventing any unbalancing from occuring which may result in unwanted movement of the cutting tool carrying motor housing. Additionally, because the router of the present invention utilizes the engagement between the circumference of the motor housing and a bore provided in an annular upstanding portion of a base to guide the vertical movement of the motor housing during operation and the clamping mechanism acts over substantially this entire relatively large surface area, it is substantially more resistant to wear which may result in unsatisfactory performance.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.